The strongest predictor of whether a woman would continue breastfeeding was whether or not she returned to work within 6 weeks of delivery, the researchers found; those who did were 3.4 times more likely to stop breastfeeding than those who had longer leaves.

The risk of not establishing breastfeeding was also more than doubled among mothers who went back to work between 6 to 12 weeks after delivery compared to the women who were still not working.

Women who were managers, had flexible work schedules, and had more job autonomy were more likely to start breastfeeding their infants, and were more likely to breastfeed longer.

While the U.S. requires employers with 50 or more workers to offer them 12 weeks of unpaid, job-protected maternity leave, Guendelman and her team note, “many nonaffluent workers do not take leave because they cannot forego pay, are not covered, or are unaware of their eligibility, and that can be very stressful.”

The findings, they add, suggest that “merely establishing maternity leave policies without encouraging their use and making them economically feasible do not suffice to promote breastfeeding success.”

Canada recently extended its paid maternity leave from 6 months to 1 year, Guendelman noted in an interview. “Studies in Canada evaluating this policy are showing that breastfeeding increases by about one third of a month with every additional month that the mom is not at work,” she said.